src/raw.rs - anymap blob - Chris Morgan’s Git repositories

   1 //! The raw form of a `Map`, allowing untyped access.
   2 //!
   3 //! All relevant details are in the `RawMap` struct.
   4
   5 use std::any::TypeId;
   6 use std::borrow::Borrow;
   7 use std::collections::hash_map::{self, HashMap};
   8 use std::hash::Hash;
   9 use std::hash::{Hasher, BuildHasherDefault};
  10 use std::mem;
  11 use std::ops::{Index, IndexMut};
  12 use std::ptr;
  13
  14 use any::{Any, UncheckedAnyExt};
  15
  16 #[derive(Default)]
  17 struct TypeIdHasher {
  18     value: u64,
  19 }
  20
  21 impl Hasher for TypeIdHasher {
  22     #[inline(always)]
  23     fn write(&mut self, bytes: &[u8]) {
  24         // This expects to receive one and exactly one 64-bit value
  25         debug_assert!(bytes.len() == 8);
  26         unsafe {
  27             ptr::copy_nonoverlapping(mem::transmute(&bytes[0]), &mut self.value, 1)
  28         }
  29     }
  30
  31     #[inline(always)]
  32     fn finish(&self) -> u64 { self.value }
  33 }
  34
  35 #[test]
  36 fn type_id_hasher() {
  37     fn verify_hashing_with(type_id: TypeId) {
  38         let mut hasher = TypeIdHasher::default();
  39         type_id.hash(&mut hasher);
  40         assert_eq!(hasher.finish(), unsafe { mem::transmute::<TypeId, u64>(type_id) });
  41     }
  42     // Pick a variety of types, just to demonstrate it’s all sane. Normal, zero-sized, unsized, &c.
  43     verify_hashing_with(TypeId::of::<usize>());
  44     verify_hashing_with(TypeId::of::<()>());
  45     verify_hashing_with(TypeId::of::<str>());
  46     verify_hashing_with(TypeId::of::<&str>());
  47     verify_hashing_with(TypeId::of::<Vec<u8>>());
  48 }
  49
  50 /// The raw, underlying form of a `Map`.
  51 ///
  52 /// At its essence, this is a wrapper around `HashMap<TypeId, Box<Any>>`, with the portions that
  53 /// would be memory-unsafe removed or marked unsafe. Normal people are expected to use the safe
  54 /// `Map` interface instead, but there is the occasional use for this such as iteration over the
  55 /// contents of an `Map`. However, because you will then be dealing with `Any` trait objects, it
  56 /// doesn’t tend to be so very useful. Still, if you need it, it’s here.
  57 #[derive(Debug)]
  58 pub struct RawMap<A: ?Sized + UncheckedAnyExt = Any> {
  59     inner: HashMap<TypeId, Box<A>, BuildHasherDefault<TypeIdHasher>>,
  60 }
  61
  62 // #[derive(Clone)] would want A to implement Clone, but in reality it’s only Box<A> that can.
  63 impl<A: ?Sized + UncheckedAnyExt> Clone for RawMap<A> where Box<A>: Clone {
  64     fn clone(&self) -> RawMap<A> {
  65         RawMap {
  66             inner: self.inner.clone(),
  67         }
  68     }
  69 }
  70
  71 impl<A: ?Sized + UncheckedAnyExt> Default for RawMap<A> {
  72     fn default() -> RawMap<A> {
  73         RawMap::new()
  74     }
  75 }
  76
  77 impl_common_methods! {
  78     field: RawMap.inner;
  79     new() => HashMap::with_hasher(Default::default());
  80     with_capacity(capacity) => HashMap::with_capacity_and_hasher(capacity, Default::default());
  81 }
  82
  83 /// RawMap iterator.
  84 #[derive(Clone)]
  85 pub struct Iter<'a, A: ?Sized + UncheckedAnyExt> {
  86     inner: hash_map::Iter<'a, TypeId, Box<A>>,
  87 }
  88 impl<'a, A: ?Sized + UncheckedAnyExt> Iterator for Iter<'a, A> {
  89     type Item = &'a A;
  90     #[inline] fn next(&mut self) -> Option<&'a A> { self.inner.next().map(|x| &**x.1) }
  91     #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
  92 }
  93 impl<'a, A: ?Sized + UncheckedAnyExt> ExactSizeIterator for Iter<'a, A> {
  94     #[inline] fn len(&self) -> usize { self.inner.len() }
  95 }
  96
  97 /// RawMap mutable iterator.
  98 pub struct IterMut<'a, A: ?Sized + UncheckedAnyExt> {
  99     inner: hash_map::IterMut<'a, TypeId, Box<A>>,
 100 }
 101 impl<'a, A: ?Sized + UncheckedAnyExt> Iterator for IterMut<'a, A> {
 102     type Item = &'a mut A;
 103     #[inline] fn next(&mut self) -> Option<&'a mut A> { self.inner.next().map(|x| &mut **x.1) }
 104     #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
 105 }
 106 impl<'a, A: ?Sized + UncheckedAnyExt> ExactSizeIterator for IterMut<'a, A> {
 107     #[inline] fn len(&self) -> usize { self.inner.len() }
 108 }
 109
 110 /// RawMap move iterator.
 111 pub struct IntoIter<A: ?Sized + UncheckedAnyExt> {
 112     inner: hash_map::IntoIter<TypeId, Box<A>>,
 113 }
 114 impl<A: ?Sized + UncheckedAnyExt> Iterator for IntoIter<A> {
 115     type Item = Box<A>;
 116     #[inline] fn next(&mut self) -> Option<Box<A>> { self.inner.next().map(|x| x.1) }
 117     #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
 118 }
 119 impl<A: ?Sized + UncheckedAnyExt> ExactSizeIterator for IntoIter<A> {
 120     #[inline] fn len(&self) -> usize { self.inner.len() }
 121 }
 122
 123 /// RawMap drain iterator.
 124 pub struct Drain<'a, A: ?Sized + UncheckedAnyExt> {
 125     inner: hash_map::Drain<'a, TypeId, Box<A>>,
 126 }
 127 impl<'a, A: ?Sized + UncheckedAnyExt> Iterator for Drain<'a, A> {
 128     type Item = Box<A>;
 129     #[inline] fn next(&mut self) -> Option<Box<A>> { self.inner.next().map(|x| x.1) }
 130     #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
 131 }
 132 impl<'a, A: ?Sized + UncheckedAnyExt> ExactSizeIterator for Drain<'a, A> {
 133     #[inline] fn len(&self) -> usize { self.inner.len() }
 134 }
 135
 136 impl<A: ?Sized + UncheckedAnyExt> RawMap<A> {
 137     /// An iterator visiting all entries in arbitrary order.
 138     ///
 139     /// Iterator element type is `&Any`.
 140     #[inline]
 141     pub fn iter(&self) -> Iter<A> {
 142         Iter {
 143             inner: self.inner.iter(),
 144         }
 145     }
 146
 147     /// An iterator visiting all entries in arbitrary order.
 148     ///
 149     /// Iterator element type is `&mut Any`.
 150     #[inline]
 151     pub fn iter_mut(&mut self) -> IterMut<A> {
 152         IterMut {
 153             inner: self.inner.iter_mut(),
 154         }
 155     }
 156
 157     /// Clears the map, returning all items as an iterator.
 158     ///
 159     /// Iterator element type is `Box<Any>`.
 160     ///
 161     /// Keeps the allocated memory for reuse.
 162     #[inline]
 163     pub fn drain(&mut self) -> Drain<A> {
 164         Drain {
 165             inner: self.inner.drain(),
 166         }
 167     }
 168
 169     /// Gets the entry for the given type in the collection for in-place manipulation.
 170     pub fn entry(&mut self, key: TypeId) -> Entry<A> {
 171         match self.inner.entry(key) {
 172             hash_map::Entry::Occupied(e) => Entry::Occupied(OccupiedEntry {
 173                 inner: e,
 174             }),
 175             hash_map::Entry::Vacant(e) => Entry::Vacant(VacantEntry {
 176                 inner: e,
 177             }),
 178         }
 179     }
 180
 181     /// Returns a reference to the value corresponding to the key.
 182     ///
 183     /// The key may be any borrowed form of the map's key type, but `Hash` and `Eq` on the borrowed
 184     /// form *must* match those for the key type.
 185     pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&A>
 186     where TypeId: Borrow<Q>, Q: Hash + Eq {
 187         self.inner.get(k).map(|x| &**x)
 188     }
 189
 190     /// Returns true if the map contains a value for the specified key.
 191     ///
 192     /// The key may be any borrowed form of the map's key type, but `Hash` and `Eq` on the borrowed
 193     /// form *must* match those for the key type.
 194     pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool
 195     where TypeId: Borrow<Q>, Q: Hash + Eq {
 196         self.inner.contains_key(k)
 197     }
 198
 199     /// Returns a mutable reference to the value corresponding to the key.
 200     ///
 201     /// The key may be any borrowed form of the map's key type, but `Hash` and `Eq` on the borrowed
 202     /// form *must* match those for the key type.
 203     pub fn get_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut A>
 204     where TypeId: Borrow<Q>, Q: Hash + Eq {
 205         self.inner.get_mut(k).map(|x| &mut **x)
 206     }
 207
 208     /// Inserts a key-value pair from the map. If the key already had a value present in the map,
 209     /// that value is returned. Otherwise, None is returned.
 210     ///
 211     /// It is the caller’s responsibility to ensure that the key corresponds with the type ID of
 212     /// the value. If they do not, memory safety may be violated.
 213     pub unsafe fn insert(&mut self, key: TypeId, value: Box<A>) -> Option<Box<A>> {
 214         self.inner.insert(key, value)
 215     }
 216
 217     /// Removes a key from the map, returning the value at the key if the key was previously in the
 218     /// map.
 219     ///
 220     /// The key may be any borrowed form of the map's key type, but `Hash` and `Eq` on the borrowed
 221     /// form *must* match those for the key type.
 222     pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<Box<A>>
 223     where TypeId: Borrow<Q>, Q: Hash + Eq {
 224         self.inner.remove(k)
 225     }
 226
 227 }
 228
 229 impl<A: ?Sized + UncheckedAnyExt, Q> Index<Q> for RawMap<A> where TypeId: Borrow<Q>, Q: Eq + Hash {
 230     type Output = A;
 231
 232     fn index<'a>(&'a self, index: Q) -> &'a A {
 233         self.get(&index).expect("no entry found for key")
 234     }
 235 }
 236
 237 impl<A: ?Sized + UncheckedAnyExt, Q> IndexMut<Q> for RawMap<A> where TypeId: Borrow<Q>, Q: Eq + Hash {
 238     fn index_mut<'a>(&'a mut self, index: Q) -> &'a mut A {
 239         self.get_mut(&index).expect("no entry found for key")
 240     }
 241 }
 242
 243 impl<A: ?Sized + UncheckedAnyExt> IntoIterator for RawMap<A> {
 244     type Item = Box<A>;
 245     type IntoIter = IntoIter<A>;
 246
 247     fn into_iter(self) -> IntoIter<A> {
 248         IntoIter {
 249             inner: self.inner.into_iter(),
 250         }
 251     }
 252 }
 253
 254 /// A view into a single occupied location in a `RawMap`.
 255 pub struct OccupiedEntry<'a, A: ?Sized + UncheckedAnyExt> {
 256     inner: hash_map::OccupiedEntry<'a, TypeId, Box<A>>,
 257 }
 258
 259 /// A view into a single empty location in a `RawMap`.
 260 pub struct VacantEntry<'a, A: ?Sized + UncheckedAnyExt> {
 261     inner: hash_map::VacantEntry<'a, TypeId, Box<A>>,
 262 }
 263
 264 /// A view into a single location in a `RawMap`, which may be vacant or occupied.
 265 pub enum Entry<'a, A: ?Sized + UncheckedAnyExt> {
 266     /// An occupied Entry
 267     Occupied(OccupiedEntry<'a, A>),
 268     /// A vacant Entry
 269     Vacant(VacantEntry<'a, A>),
 270 }
 271
 272 impl<'a, A: ?Sized + UncheckedAnyExt> Entry<'a, A> {
 273     /// Ensures a value is in the entry by inserting the default if empty, and returns
 274     /// a mutable reference to the value in the entry.
 275     ///
 276     /// It is the caller’s responsibility to ensure that the key of the entry corresponds with
 277     /// the type ID of `value`. If they do not, memory safety may be violated.
 278     pub unsafe fn or_insert(self, default: Box<A>) -> &'a mut A {
 279         match self {
 280             Entry::Occupied(inner) => inner.into_mut(),
 281             Entry::Vacant(inner) => inner.insert(default),
 282         }
 283     }
 284
 285     /// Ensures a value is in the entry by inserting the result of the default function if empty,
 286     /// and returns a mutable reference to the value in the entry.
 287     ///
 288     /// It is the caller’s responsibility to ensure that the key of the entry corresponds with
 289     /// the type ID of `value`. If they do not, memory safety may be violated.
 290     pub unsafe fn or_insert_with<F: FnOnce() -> Box<A>>(self, default: F) -> &'a mut A {
 291         match self {
 292             Entry::Occupied(inner) => inner.into_mut(),
 293             Entry::Vacant(inner) => inner.insert(default()),
 294         }
 295     }
 296 }
 297
 298 impl<'a, A: ?Sized + UncheckedAnyExt> OccupiedEntry<'a, A> {
 299     /// Gets a reference to the value in the entry.
 300     pub fn get(&self) -> &A {
 301         &**self.inner.get()
 302     }
 303
 304     /// Gets a mutable reference to the value in the entry.
 305     pub fn get_mut(&mut self) -> &mut A {
 306         &mut **self.inner.get_mut()
 307     }
 308
 309     /// Converts the OccupiedEntry into a mutable reference to the value in the entry
 310     /// with a lifetime bound to the collection itself.
 311     pub fn into_mut(self) -> &'a mut A {
 312         &mut **self.inner.into_mut()
 313     }
 314
 315     /// Sets the value of the entry, and returns the entry's old value.
 316     ///
 317     /// It is the caller’s responsibility to ensure that the key of the entry corresponds with
 318     /// the type ID of `value`. If they do not, memory safety may be violated.
 319     pub unsafe fn insert(&mut self, value: Box<A>) -> Box<A> {
 320         self.inner.insert(value)
 321     }
 322
 323     /// Takes the value out of the entry, and returns it.
 324     pub fn remove(self) -> Box<A> {
 325         self.inner.remove()
 326     }
 327 }
 328
 329 impl<'a, A: ?Sized + UncheckedAnyExt> VacantEntry<'a, A> {
 330     /// Sets the value of the entry with the VacantEntry's key,
 331     /// and returns a mutable reference to it
 332     ///
 333     /// It is the caller’s responsibility to ensure that the key of the entry corresponds with
 334     /// the type ID of `value`. If they do not, memory safety may be violated.
 335     pub unsafe fn insert(self, value: Box<A>) -> &'a mut A {
 336         &mut **self.inner.insert(value)
 337     }
 338 }